This invention relates to novel coatings for thermoplastic articles. More particularly, the invention relates to novel ultraviolet light-absorbing melamine-polyol coatings.
Melamine-polyol coatings are used to provide abrasion and solvent resistance to thermoplastic substrates. These coatings sometimes include UV absorbers to protect the substrates from UV degradation which can cause yellowing, embrittlement, and coating adhesion failure. A problem which has been encountered with respect to these coatings is that conventional UV-absorbing compounds are sometimes too volatile or unstable to be retained in the coatings at elevated temperatures over prolonged times. U.S. Pat. No. 4,197,392 describes a coating formed from a melamine nucleus compound, a polyol and a benzophenone derivative as a UV absorber. In this coating, the UV absorber reacts with the melamine nucleus to form a non-volatile absorber.
A need continues to exist for melamine-polyol coatings which have high UV absorptivities and which maintain such absorptivities at elevated temperatures.